I am currently trying to become a Christian Wiccan. I am trying to learn more about the meanings of the holidays. I know most all of them. If you know any meanings of these or other holidays please help me out! Also, if you knew the dates for these or other holidays for the northern hemisphere that too would help!
Samhain.
Imbolc.
Beltane.
Lughnasadh.
Ostara.
Yule.
Litha.
Mabon.

There's an excellent website that discusses the various Sabbats at http://www.witchessabbats.com/ I highly recommend the information there. As for the dates in the Northern Hemisphere, they fall thusly:

Yule - Dec 21-23

Imbolc - Feb 2

Oestara - Mar 21-23

Beltane - May 1

Midsummer/Litha - June 21-23

Lammas/Lughnassad - Aug 1

Mabon - Sep 21-23

Samhain - Oct 31

The Sabbats, known collectively as the Wheel of the Year mark not only the changing seasons, but also the cycles in the relationship of the God and the Goddess, and the cycles of birth and death.